Source selection for conference bridges

ABSTRACT

The present invention provides an audio source selection process for a conference bridge. The conference bridge receives multiple audio sources and selects at least one of the audio sources based on the relative signal levels associated with the audio signal at each of the audio sources. The audio signals associated with the selected source are delivered to conference participants via one or more audio outputs. The conference bridge will repeatedly employ a selection process to select an audio source based on signal level measurements for the audio signals of the audio sources. During the selection process, the influence of a selected audio source relative to the other unselected audio sources is reduced, after the selected audio source has remained selected for more than a first time period.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/152,529, filed Jun. 3, 2011, entitled “SOURCE SELECTION FORCONFERENCE BRIDGES,” which is a continuation of U.S. patent applicationSer. No. 11/553,750, filed Oct. 27, 2006, entitled “SOURCE SELECTION FORCONFERENCE BRIDGES,” now U.S. Pat. No. 7,957,512, the disclosures ofwhich are both hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to conference bridges, and in particularto selecting audio sources during a conference call.

BACKGROUND OF THE INVENTION

Conference bridges are used to facilitate conference calls between twoor more conference participants. In operation, multiple calls frommultiple communication devices are terminated at a conference bridge.The audio levels for the audio signals from the different communicationdevices are monitored and used to identify a particular one of the audiosignals to provide as an output to the communication devices. Ingeneral, the communication terminal providing the audio signal havingthe highest level at any given time is selected as the selectedcommunication terminal. The audio signal from the selected communicationterminal is provided to the communication devices in the conference. Theaudio signals from the unselected communication terminals are notprovided to the communication devices. Only the audio signal provided bythe selected communication terminal is presented to the other unselectedcommunication terminals. As such, none of the participants will hear anyparticipants other than those using the selected communication terminal.To avoid distractions, the audio signal from the selected communicationterminal is generally not provided back to the selected communicationterminal.

Since conference bridges generally select the audio signals from theloudest participant to present to other participants, there are manysituations where other participants are contending for conference timeto no avail. If those participants contending for conference time do notpresent audio signals at a level higher than the participant using thecurrently selected communication terminal, they will never be selectedas the selected participant. This situation is problematic forsoft-spoken participants as well as participants in a conference with arelatively active and loud participant. In many instances, a louderparticipant may gain conference access and maintain conference accessfor extended periods of time, even though other participants arecontending for conference access.

Further, conference calls are being employed in more diverseapplications. For instance, on-line gaming groups are employingconference calls to allow multiple garners from different locations totalk with each other during a gaming session. Given the excitement andpotential for significant background music or other noise, those garnerswith the louder group or environment may dominate the conference simplydue to the selection process used by the conference bridge hosting theconference call. Again, the louder participants may gain conferenceaccess and maintain conferences access for extended periods of time,even though other participants want conference access.

Accordingly, there is a need for a conference bridge that providesgreater conference access to those participants who are contending forconference time against louder participants or participants inrelatively noisy environments. There is a further need to ensure thatlouder participants or participants in noisy environments do notmaintain conference access for extended periods of time when otherparticipants are contending for conference access.

SUMMARY OF THE INVENTION

The present invention provides an audio source selection process for aconference bridge. The conference bridge receives multiple audio sourcesand selects at least one of the audio sources based on the relativesignal levels associated with the audio signal at each of the audiosources. The audio signals associated with the selected source aredelivered to conference participants via one or more audio outputs. Eachaudio source is associated with an audio output to facilitatebidirectional communications for each conference participant. Further,the audio signals of the selected audio source are generally notdelivered via an audio output corresponding to the selected audiosource. The conference bridge will repeatedly employ a selection processto select an audio source based on signal level measurements for theaudio signals of the audio sources. During the selection process, theinfluence of a selected audio source relative to the unselected audiosources is reduced, after the selected audio source has remainedselected for more than a first time period. By reducing the relativeinfluence of the selected audio source after a certain period of time,the likelihood of selecting another audio source that is contending forselection increases.

Those skilled in the art will appreciate the scope of the presentinvention and realize additional aspects thereof after reading thefollowing detailed description of the preferred embodiments inassociation with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a block representation of a communication environmentaccording to one embodiment of the present invention.

FIG. 2 is a block representation of a conference bridge according to oneembodiment of the present invention.

FIGS. 3A and 3B provide a flow diagram illustrating operation of aconference bridge according to one embodiment of the present invention.

FIG. 4 is a graph providing an exemplary weighting factor to apply tolevel measurements associated with sources that have been selected formore than a first time period.

FIG. 5 is a block representation of a video bridge portion of aconference bridge according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the invention and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

The present invention provides a unique audio source selection processfor a conference bridge. The conference bridge receives multiple audiosources and selects at least one of the audio sources based on therelative signal levels associated with the audio signal at each of theaudio sources. The audio signals associated with the selected source aredelivered to conference participants via one or more audio outputs. Eachaudio source is associated with an audio output to facilitatebidirectional communications for each conference participant. Further,the audio signals of the selected audio source are generally notdelivered via an audio output corresponding to the selected audiosource. The conference bridge will repeatedly employ a selection processto select an audio source based on signal level measurements for theaudio signals of the audio sources. During the selection process, theinfluence of a selected audio source relative to the unselected audiosources is reduced, after the selected audio source has remainedselected for more than a first time period. By reducing the relativeinfluence of the selected audio source after a certain period of time,the likelihood of selecting another audio source that is contending forselection increases.

During the first time period, each of the audio sources generallycompetes equally for selection. The influence of the selected audiosource relative to the unselected audio sources may be continuallyreduced after the first time period, if the selected audio sourceremains selected. A further reduction may be employed for each selectioniteration or after a defined number of selection iterations. Reductionof the influence of the selected audio source relative to the unselectedaudio sources may continue indefinitely or stop at a defined level.Alternatively, the influence of the selected audio source relative tothe unselected audio sources may be reduced by a single step or bysuccessive steps during subsequent time periods, if the selected audiosource remains selected for more than a first time period. Once reduced,the influence of the selected audio source relative to the unselectedaudio source may remain reduced for a set period of time after anotheraudio source is selected.

To reduce the influence of the selected audio source relative to theunselected audio sources, a weighting factor may be used to reduce asignal level measurement of the selected audio source for the selectionprocess. Alternatively, weighting factors may be applied to increase thesignal level measurements of the selected audio sources. After a sourcehas remained selected for the first time period, the weighting factorsmay be adjusted after each iteration or number of iterations for theselection process to reduce the influence of the signal levelmeasurements of the selected source relative to the signal levelmeasurements of the unselected sources. For video conferencingapplications, the selection process provided for the audio portion ofthe conference may be used to select a video source.

Prior to delving into the details of the present invention, an overviewof a conference environment 10 is provided in association with FIG. 1.As illustrated, any number of communication terminals 12 (1-N) may callinto a conference bridge 14 over a communication network 16 tofacilitate a conference call among the various users associated with thecommunication terminals 12. Typically, the conference bridge 14 willselect one of the communication terminals 12 as a selected communicationterminal 12, and deliver the audio received from the selectedcommunication terminal 12 to the remaining communication terminals 12participating in the conference call. For example, if communicationterminal 12(1) was selected as the selected communication terminal 12,the audio signal received from communication terminal 12(1) is providedto the other communication terminals 12(2-N), assuming thatcommunication terminals (1-N) are participating in the conference call.Generally, the audio received from the selected communication terminal12(1) is not provided back to the selected communication terminal 12(1)to avoid distracting the conference participant associated with theselected communication terminal 12(1).

The present invention provides a selection process for selecting theselected communication terminal 12 from the participating communicationterminals 12(1-N). An overview of a basic selection process is providedin association with the description of the architecture of a conferencebridge 14, which is illustrated in FIG. 2. As depicted, audio signalsfrom the various communication terminals 12(1-N) are ultimately receivedby the conference bridge 14 as sources 1-N, respectively. The audiosignals provided to the communication terminals 12(1-N) are representedas outputs 1-N, respectively. As such, source N and output N providebidirectional communications for communication terminal 12(N).

During operation, audio signals from the various communication terminals12(1-N) are received as sources 1-N and processed by signalnormalization circuitry 18(1-N). The signal normalization circuitry 18may operate on the various audio signals to provide a normalized signallevel among the conference participants, such that the relative volumeassociated with each of the conference participants during theconference call is substantially normalized to a given level. The signalnormalization circuitry 18 is optional, but normally employed inconference bridges 14. After normalization, the audio signals from thevarious sources 1-N are sent to an audio processing function 20. Asource selection function 22 is used to select one of the sources 1-N asa selected source, and provide a corresponding source selection signalto the audio processing function 20. In response to the source selectionsignal, the audio processing function 20 will deliver the audio signalfor the selected source (1-N) over all of the outputs, except for theoutput associated with the selected source. If source N is the selectedsource, the audio processing function 20 will provide the audio signalfrom source N to outputs 1 through N-1. The audio signals from thenon-selected sources 1 through N-1 is dropped, and therefore notpresented to any of the outputs 1-N, in traditional fashion.

In general, the source providing the audio signal having the greatestmagnitude is selected. The source selection function 22 willcontinuously monitor the relative magnitudes of the audio signals ateach of the sources 1-N, and select a source throughout the conferencecall. As such, the source selection function 22 will select differentones of the sources 1-N throughout the conference call.

After normalization by the signal normalization circuitry 18(1-N), theaudio signals for sources 1-N are provided to corresponding leveldetection circuitry 24(1-N). Each level detection circuitry 24 willprocess a corresponding audio signal to generate a level measurementsignal, which is presented to the source selection function 22. Thelevel measurement signal corresponds to a relative magnitude of theaudio signal for a given source. The level detection circuitry 24 mayemploy different techniques to generate a corresponding levelmeasurement signal. In one embodiment, a power level derived from arunning average of a given audio signal or an average power level of anaudio signal over a given period of time is generated and represents thelevel measurement signal, which is provided by the level detectioncircuitry 24 to the source selection function 22. The source selectionfunction 22 will continuously monitor the level measurement signals fromthe various level detection circuitry 24(1-N) and select one of thesources 1-N as a selected source based thereon. As noted, the sourceselection function 22 will then provide a source selection signal toidentify the selected source to the audio processing function 20, whichwill deliver the audio for the selected source over the outputsassociated with the unselected sources. The output corresponding to theselected source may not be provided with an audio signal from theselected source.

The present invention lies in the selection process for determining theselected source. In general, the selection process provided by thesource selection function 22 operates to reduce the influence of theselected source relative to the unselected sources after the selectedsource has remained selected for a first time period. Reducing theinfluence of the selected source relative to the unselected sourcesincreases the likelihood that an unselected source contending forselection will be selected, even if the signal levels of the selectedsource remain at levels higher than those of the source contending forselection. Therefore, conference participants that tend to speak moresoftly than other conference participants, or are in quieter overallenvironments, are given a greater chance to participate in theconference. In other words, conference participants who speak moreloudly or are located in a noisier environment will not dominate theconference simply because of their relative volume.

With reference to FIGS. 3A and 3B, the source selection function 22 willbegin a source selection process (step 100) by receiving levelmeasurements associated with the audio signals for the active sources1-N (step 102). The level measurements may be received via the levelmeasurement signals provided by the level detection circuitry 24(1-N),which monitors the audio signals of the sources 1-N and providecorresponding level measurement signals to the source selection function22. The source selection function 22 will substantially continuouslyreceive level measurements for the sources.

The source selection function 22 will then determine how long theselected source has been selected, assuming that the process has runbefore and a selected source has been selected from the active sources(step 104). The level measurements may be used as is, or weightedversions of the level measurements may be used, as will be describedbelow.

If the selected source has been selected for less than a first time, thedetermination of the selected source will be based on unadjusted, orunweighted, level measurements (step 104A). As such, the sourceselection function 22 will select a source from the active sources basedon the level measurements, which are essentially the level measurements(step 106). As such, none of the sources are prioritized with respect toanother during the source selection process.

If the selected source has been selected between a first time and asecond time, the influence of the selected source is reduced relative tothe influence of the unselected sources. For example, if the selectedsource has been selected between a first time and a second time period,one or more of the level measurements are weighted to systematicallyreduce the influence of the level measurement for the selected sourcerelative to the level measurements of the unselected sources between thefirst time and the second time (step 104B). To inject such influence,the level measurement of the selected source may be reduced by aweighting factor. Alternatively, the level measurements for theunselected sources may be increased by a weighting factor. Those skilledin the art will recognize various techniques for reducing the influenceof the selected source relative to the unselected sources during thesource selection process. Once the weighting is applied to one or moreof the level measurements, one of the sources is chosen as the selectedsource based on the level measurements (step 106).

Between the first time and the second time, the relative influence ofthe selected source on the source selection process may continuallydecline with each source selection iteration. Alternatively, theinfluence may be continually reduced in a stepwise fashion after aselect number of iterations throughout the period between the first andsecond times. Further, the influence may be reduced once or any numberof times between the first and second times.

If the selected source has been selected longer than the second time,one or more of the level measurements are weighted to reduce theinfluence of the level measurement for the selected source relative tothe level measurements of the unselected sources by a fixed factor (step104C). As such, the reduction of the influence of the selected sourcerelative to the unselected sources during the selection process may stopafter a certain period of time or amount of reduction has been reached.Again, once the level measurements have been determined from weightingone or more of the level measurements, the source selection function 22may select a source based on the level measurements (step 106).

After a source has been selected, a selection delay may be provided(step 108) and the process will repeat if the conference call remainsselected. As such, the source selection function 22 will determine ifthe conference call is still selected (step 110), and if the call is nolonger active the source selection process will end (step 112). If theconference call is still active (step 110), the source selectionfunction 22 will maintain a time for which the selected source has beenselected (step 114), and repeat the process by returning to step 102(step 116).

The source selection process will run in a substantially continuousfashion. For example, the selection process may repeat every 5-10 ms.However, the time that a source has been selected is maintained from oneiteration to the next. If the selected source has remained selected fora certain period of time, which will encompass multiple source selectioniterations, steps are taken to reduce the influence of the selectedsource with respect to the unselected sources in an effort to increase alikelihood of an unselected source that is contending for selectionbeing selected after the first time period.

Those skilled in the art will recognize that the process described aboveis merely exemplary, and that the reduction of influence for an selectedsource in the source selection process may take many forms. For example,the reduction may employ a single reduction, wherein the extent of thereduction increases over time. Further, the amount of reduction need notlevel off after the second time.

With reference to FIG. 4, a chart is provided to illustrate theweighting factors to provide to a selection level measurement for aselected source when the source remains selected for more than 30seconds. When the selected source has been selected for less than 15seconds, all of the sources will contend equally for selection. When theselected source has been selected for more than 15 seconds but less than30 seconds, the weighting factor applied to the level measurement forthe selected source gradually declines, such that the selected source isgiven less priority with respect to the unselected sources during thesource selection process. After 30 seconds of being selected as theselected source, the weighting factor for the level measurement of theselected source is fixed, and will remain so until another source isselected. Notably, after the influence of the selected source is reducedrelative to the unselected sources, the influence reduction may remainin whole or may be progressively eliminated over a period of time afteranother source is selected. This will prevent the formerly selectedsource from regaining selected source status too quickly.

With reference to FIG. 5, the audio bridge 14 may be used to selectvideo sources when a video conferencing function is available. In manyinstances, the video source selection will track that of the audiosource selection. As such, a video processing function 26 may beprovided, where video sources 1-N correspond to sources 1-N. Further,each video source 1-N will be associated with a video output 1-N. Thevideo processing function 26 will receive video signals from the videosources 1-N, and provide a video signal for a selected one of the videosources 1-N to each of the video outputs 1-N. The video signals for theunselected video sources may be dropped or processed in an appropriatevideo conferencing fashion. For the present invention, the sourceselection function 22 of the audio bridge 14 may use the sourceselection process described above to provide a source selection signalto the video processing function 26. Notably, the video source selectionmay be based on the audio signals from the sources 1-N of the audiobridge 14, and as such, will select the video source corresponding tothe selected audio source.

Although the above embodiments focus on selecting a single source at anygiven time during a conference call, multiple sources may be selected atthe same time. The corresponding audio signals for the selected sourcesmay be mixed and provided to each of the outputs associated with theunselected sources. The audio signal for one selected source may beprovided over the output of the other selected sources, such thatparticipants associated with the multiple selected sources can hear eachother, but preferably not themselves. The selection process describedabove is equally applicable when multiple sources are selected.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present invention. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

What is claimed is:
 1. A method for providing media source selection fora media conference, comprising: receiving respective informationcharacterizing audio content from each of a plurality of media sourcesfor a conference call, the plurality of media sources comprising atleast one media source selected for a current time interval and at leastone media source not selected for the current time interval; determininghow long each of the at least one media source selected for the currenttime interval has been a selected media source; when one or more of theat least one media source selected for the current time interval hasbeen selected for longer than a predetermined duration, weighting therespective information characterizing the audio content from the one ormore of the at least one media source that has been selected for longerthan the predetermined duration to reduce an influence of respectiveinformation characterizing the audio content from the one or more of theat least one media source selected for more than the predeterminedduration relative to respective information characterizing audio contentfrom any media source not selected for more than the predeterminedduration; selecting for a next time interval at least one media sourcefrom the plurality of media sources based on the respective informationcharacterizing the audio content from the plurality of media sources andthe weighting of the respective information characterizing the audiocontent from the one or more of the at least one media source that hasbeen selected for longer than the predetermined duration; and providing,to at least one output for the conference call, a respective mediasignal for the at least one media source selected for the next timeinterval.
 2. The method of claim 1, wherein the step of selecting forthe next time interval the at least one selected media source comprisesselecting a plurality of media sources.
 3. The method of claim 1,wherein the respective information characterizing the audio content fromeach media source comprises information characterizing an audio signalfrom the media source.
 4. The method of claim 3, wherein the informationcharacterizing each audio signal comprises a respective audio levelmeasurement.
 5. The method of claim 4, wherein weighting the respectiveinformation characterizing the audio content from the one or more of theat least one media source that has been selected for longer than thepredetermined duration comprises decreasing the audio level measurementfor that source by a weighting factor.
 6. The method of claim 4, whereinweighting the respective information characterizing the audio contentfrom the one or more of the at least one media source that has beenselected for longer than the predetermined duration comprises increasingan audio level measurement for at least one audio signal of a mediasource not selected for longer than the predetermined duration by atleast one weighting factor.
 7. The method of claim 1, wherein theinfluence of respective information characterizing the audio contentfrom the at least one media source selected for the current timeinterval relative to respective information characterizing the audiocontent from the any media source not selected for longer than thepredetermined duration is continually reduced after the predeterminedduration.
 8. The method of claim 1, wherein the influence of therespective information characterizing the audio content from the one ormore of the at least one media source selected for longer than thepredetermined duration relative to the respective informationcharacterizing the audio content from the any media source not selectedfor longer than the predetermined duration is reduced after the currenttime interval as long as the at least one media source remains selected.9. The method of claim 1, wherein the influence of the respectiveinformation characterizing the audio content from the one or more of theat least one media source selected for longer than the predeterminedduration relative to the respective information characterizing the audiocontent from the any media source not selected for longer than thepredetermined duration is continually reduced after the predeterminedduration as long as the one or more of the at least one media sourceselected for longer than the predetermined duration remains selected.10. The method of claim 1, wherein the influence of the respectiveinformation characterizing the audio content from the one or more of theat least one media source selected for longer than the predeterminedduration relative to the respective information characterizing the audiocontent from the any media source not selected for longer than thepredetermined duration is continually reduced during a defined periodafter the current time interval.
 11. The method of claim 7, wherein theinfluence of the respective information characterizing the audio contentfrom the one or more of the at least one media source selected forlonger than the predetermined duration relative to the respectiveinformation characterizing the audio content from the any media sourcenot selected for longer than the predetermined duration is not furtherreduced after the predetermined duration.
 12. The method of claim 1,wherein the influence of the respective information characterizing theaudio content from the one or more of the at least one media sourceselected for longer than the predetermined duration relative to therespective information characterizing the audio content from the anymedia source not selected for longer than the predetermined durationremains reduced for a defined period after the one or more of the atleast one media source selected for longer than the predeterminedduration becomes an unselected media source.
 13. The method of claim 1,comprising: selecting at least one video source for the current timeinterval from a plurality of video sources associated with a pluralityof audio sources based on respective information characterizing audiocontent from each audio source and a weighting of informationcharacterizing audio content from at least one of the audio sources; andproviding at least one video signal from the at least one video sourceselected for the current time interval to at least one video output forthe conference call.
 14. The method of claim 1, wherein the mediaconference is part of an online gaming session.
 15. The method of claim1, wherein the steps of selecting media sources and providing mediasignals are performed separately for each of a plurality of outputs sothat different participants receive different selections of mediasignals.
 16. The method of claim 15, wherein each participant receives aselection of media signals that does not include a media signal from amedia source associated with that participant.
 17. The method of claim1, wherein when a plurality of media sources have been selected, themethod comprises weighting information characterizing audio content fromthe selected media sources individually based on respective lengths oftime for which each selected media source has been selected.
 18. Asystem, comprising: a plurality of input ports through which respectivemedia signals from a plurality of respective media sources are receivedfor a media conference, the plurality of respective media sourcescomprising at least one media source selected for a current timeinterval and at least one media source not selected for the current timeinterval; a source characterization element configured to receive mediasignals from the plurality of input ports and to generate respectiveinformation characterizing audio content from each media source based onits respective media signal; a source selection element configured to:receive the respective information characterizing the audio content fromeach media source; determine how long each media source selected for thecurrent time interval has been selected; when one or more of the atleast one media source selected for the current time interval has beenselected for longer than a predetermined duration, weight the respectiveinformation characterizing the audio content from the one or more of theat least one media source selected for longer than the predeterminedduration to reduce an influence of respective information characterizingthe audio content from the one or more of the at least one media sourceselected for longer than the predetermined duration relative torespective information characterizing audio content from any mediasource not selected for longer than the predetermined duration; selectat least one media source for a next time interval based on therespective information and the weighting of the respective information;and effect delivery of a media signal from the at least one media sourceselected for the next time interval to at least one output port for theconference call.
 19. The system of claim 18, wherein the sourceselection element is configured to select a plurality of media sources.20. The system of claim 18, wherein the source characterization elementis configured to make at least one audio level measurementcharacterizing audio content from at least one of the media sources. 21.The system of claim 20, wherein the source selection element isconfigured to weight the audio level measurement for audio content fromthe one or more of the at least one media source selected for longerthan the predetermined duration by decreasing a weighting of theinformation by a weighting factor.
 22. The system of claim 20, whereinthe source selection element is configured to weight the audio levelmeasurement for audio content from the one or more of the at least onemedia source selected for longer than the predetermined duration byincreasing the audio level measurement for audio content from the anymedia source not selected for longer than the predetermined duration bya respective weighting factor.
 23. The system of claim 18, wherein thesource selection element is configured to reduce the influence of therespective information characterizing the audio content from the one ormore of the at least one media source selected for longer than thepredetermined duration relative to the respective informationcharacterizing the audio content from the any media source not selectedfor longer than the predetermined duration continually after thepredetermined duration.
 24. The system of claim 18, wherein the sourceselection element is configured to reduce the influence of therespective information characterizing the audio content from the one ormore of the at least one media source selected for longer than thepredetermined duration relative to the respective informationcharacterizing the audio content from the any media source not selectedfor longer than the predetermined duration after the predeterminedduration as long as the one or more of the at least one media sourceselected for longer than the predetermined duration remains selected.25. The system of claim 18, wherein the source selection element isconfigured to reduce the influence of the respective informationcharacterizing the audio content from the one or more of the at leastone media source selected for longer than the predetermined durationrelative to the respective information characterizing the audio contentfrom the any media source not selected for longer than the predeterminedduration continually after the predetermined duration as long as the oneor more of the at least one media source selected for longer than thepredetermined duration remains selected.
 26. The system of claim 18,wherein the source selection element is configured to reduce theinfluence of the respective information characterizing the audio contentfrom the one or more of the at least one media source selected forlonger than the predetermined duration relative to the respectiveinformation characterizing the audio content from the any media sourcenot selected for longer than the predetermined duration continuallyduring a defined period after the predetermined duration.
 27. The systemof claim 26, wherein the source selection element is configured to notfurther reduce the influence of the respective informationcharacterizing the audio content from the one or more of the at leastone media source selected for longer than the predetermined durationrelative to the respective information characterizing the audio contentfrom any media source not selected for longer than the predeterminedduration after the defined period.
 28. The system of claim 18, whereinthe source selection element is configured to reduce the influence ofthe respective information characterizing the audio content from the oneor more of the at least one media source selected for longer than thepredetermined duration relative to the respective informationcharacterizing the audio content from the any media source not selectedfor longer than the predetermined duration for a defined period afterthe media source selected for longer than the predetermined durationbecomes unselected.
 29. The system of claim 18, further comprising avideo selection element configured to: select at least one selectedvideo source from a plurality of video sources associated with theplurality of input ports based on the respective informationcharacterizing the audio content from each media source and a weightingof information characterizing the audio content from at least one of themedia sources; and provide at least one respective video signal from theat least one selected video source to at least one video output for theconference call.
 30. The system of claim 18, wherein the sourceselection element is configured to select media sources and providemedia signals separately for each of a plurality of outputs so thatdifferent participants receive different selections of media signals.31. The system of claim 30, wherein the source selection element isconfigured such that each participant receives a selection of mediasignals that does not include a media signal from the media sourceassociated with that participant.
 32. The system of claim 18, whereinthe source selection element is configured, when a plurality of mediasources have been selected, to weight information characterizing audiocontent from the selected media sources individually based on respectivelengths of time for which each selected media source has been selected.